Ink jet type printing device

ABSTRACT

A print command given to a recording head section including an ink jet-type printing means is carried out by instructing the memory content of a buffer register through a print command supplying control section to a character signal generating section and deflection-controlling an output therefrom. The drive control for the recording head is effected, using a print start signal and a print end signal as an input, by a control circuit means for feeding an output to a drive motor by means of which a recording head is controllably moved in a backward direction before the printing means starts into printing operation, and controllably moved in a forward direction for a time sufficient to compensate for an initial non-uniform speed of the recording head as is encountered when the recording head starts its movement.

United States Patent [191 Suzuki Dec. 9, 1975 [73] Assignee: Casio Computer Co., Ltd., Yamato,

Japan [22] Filed: July 3, 1974 [21] Appl. No.: 485,586

Related US. Application Data [63] Continuation of Ser. No. 314,950, Dec. 14, 1972 abandoned.

[30] Foreign Application Priority Data BACK BUFFER REGISTER CONTROL gg wmo MOTOR Primary ExaminerJoseph W. Hartary Attorney, Agent, or Firm-Flynn & Frishauf [57] ABSTRACT A print command given to a recording head section including an ink jet-type printing means is carried out by instructing the memory content of a buffer register through a print command supplying control section to a character signal generating section and deflectioncontrolling an output therefrom. The drive control for the recording head is effected, using a print start signal and a print end signal as an input, by a control circuit means for feeding an output to a drive motor by means of which a recording head is controllably moved in a backward direction before the printing means starts into printing operation, and controllably moved in a forward direction for a time sufficient to compensate for an initial non-uniform speed of the recording head as is encountered when the recording head starts its movement.

5 Claims, 5 Drawing Figures CHARACTER DEFLECTION SIGNAL GENER CONTROL J' SECTION US. Patent Dec. 9, 1975 Sheet 1 of 3 3,925,787

US. Patent Dec. 9,1975 Sheet 2 of3 3,925,787

FORWARD SIGNAL BACKWARD PISXE TO PRINT COMMAND SIGNAL T CONTROL SECTION 3 I5 I? w CLOCK I L 'SIGNAL A B c D 14 SOURCE (Q2 22 F l G. 2

Q Q-H I I I2 I3 I((])Il|lllllll'lll b IIIIIIIIIIIIII (f) F l G. 3fi

(g) I J DRIVE (h) "'l I FORWARD (i) I l BACKWARD (j) L l PRINT LHOW U.S. Patent Dec. 9, 1975 Sheet 3 of3 3,925,787

DRIVE 37 41 39 SIGNAL FORWARD 43 BAC TO PRINT COMMAND SIGNAL CONTROL SECTION 3 SIGNAL 35 42 c| oc| SIGNAL :A B C D E F SOURCE (QZ' W 34 gg FIG. 4 529%?) Q |||||||||||||l HDHIIIIIIIIIIIIII (d) L I (f) L I (I) I r DRIVE (j) 1 BACKWARD (k) FORWARD (MT PRINT (m) L B BACKGROUND OF THE INVENTION The present invention relates to an ink-jet type printing device for effecting printing by moving a recording head including a printing means to jet ink droplets onto a recording paper; particularly to an ink-jet type printing device capable of effecting printing without leaving any excessive spacing on the recording paper and without involving any deformation of characters to be printed. In the conventional ink-jet type printing devices, printing is effected by moving a recording head including a printing means along a predetermined line. However, at the start and end of printing, characters tend to be deformed due to inertia encountered in moving a weighted recording head across a recording paper and due to the non-uniformity of a pump pressure etc. experienced in jetting a droplet of ink onto the recording paper. In order to avoid these drawbacks, characters should be printed on a recording paper only at uniform speed and at uniform pump pressure. In printing devices such as a hand-operated typewriter the recording head is stopped for each character, however, a certain time is required from the time a uniformly moving recording head starts its movement until the time the recording head attains its uniform speed. In addition, an excess or unnecessary spacing :is also created between characters with the result that more than necessary spacing is undesirably taken.

An object of the present invention is to provide an ink-jet type printing device capable of effecting accurate printing, from the time the recording head attains its uniform speed, without involving any excessive spacing or any deformation of characters to be printed on a recording paper.

SUMMARY OF THE INVENTION In accordance with the present invention, a control circuit controllably supplies a printing instruction signal to a recording head and a drive instruction signal to the recording head device, using a print start command signal and a print end command signal as an input. The recording head is controllably moved in a backward direction before a printing instruction is issued and then controllably moved in a forward direction for a time sufficient to rectify an initial non-uniform speed of the recording head due to inertia encountered at the start or restart of the recording head. By providing such control circuit, an accurate printing can be advantageously made without involving any excessive spacing or any deformation of characters as experienced at the start or restart and end of printing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a systematic representation of one embodiment of the present invention;

FIG. 2 shows a control circuit showing the embodiment of the present invention;

FIG. 3 shows a time chart explaining the operation of the control circuit of FIG. 2;

FIG. 4 shows another circuit diagram of the present invention; and

FIG. 5 shows a time chart explaining the operation of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, characters to be recorded on a 5 recording paper are stored in a buffer register 2 by the operation of an input section 1. The output of the buffer register 2 is connected through a print command supplying control section 3 to a character signal generating section 4, the output of which is fed, as a print command signal, to a recording head 6 through a deflection control section 5. A drive motor 7 for moving the recordinghead is controllably driven by a motor control circuit 8. The drive motor 7 is a conventional commercially available stepping motor such as that described in US. Pat. No. 3,238,399 or US. Pat. No. 3,508,091, or motor type 103-703-5 manufactured by Sanyo Electric Co., Tokyo, Japan. The motor control circuit 8 supplies drive control outputs to the (i.e., drive, forward, backward) drive motor 7. Motor control circuit 8 is a well known type of logic circuit using well known design criteria similar to that disclosed in US. Pat. No. 3,517,236. The control circuit 9 is operated by a print. starting command signal from the input section 1 and by a print ending command signal from the buffer 2, and supplies each of the instruction output signals to the motor control circuit while supplying to the print command supplying control section 3 a printing instruction signal which has a determined relation to the drive control instruction to the motor 7. The printing instruction signal (determined in relation to the drive instruction to the drive motor) is supplied as a drive signal to the drive motor before the printing operation, and after the recording head has been retracted to a position preceding a position at which a printing instruction is to be effected, that is, at which the signal is to be given to the recording head. A spacing between the position of the recording head at which a printing instruction is to be given and the position of the head at which the driving control output is fed from the motor control circuit 8 to the drive motor 7 to cause the recording head to be drivingly started, need only be sufficient to compensate for an initial nonuniform speed due to start up inertia encountered in moving the recording head. In the embodiment to be explained later, for example, the recording head is retracted, for a distance corresponding to two characters, from a print starting position; before supplying a printing instruction signal, the recording head is advanced for a distance corresponding to three characters; and printing is effected from the fourth character. In this case, there is left between words a space corresponding to one character. Retraction of the recording head in a Backward direction, for a distance corresponding to two characters from the print starting position can be effected either at the start of printing or at the restart of printing.

Referring to FIG. 2, the embodiment will be explained in which the recording head is retracted for a distance corresponding to two characters after one word is printed, and then a printing instruction is given after advancing the recording head for a distance corresponding to three characters before giving instruction to print the next successive words. To the set terminal 12 of a flip-flop circuit 11 a print starting command signal from the input section 1 shown in FIG. 1 is fed. To the reset terminal 13 a print ending command signal from the buffer register is applied. The applied as the output of the flip-flop circuit 11 is applied as the input to the first digit stage of a buffer register 14 which consists of four digit stages A, B, C and D. A conventional source 22 of clock signals and is coupled to buffer register 14. The output terminal of the first digit stage A is connected respectively to a forward control signal supplying terminal 19 and through an inverter 20 to a backward control signal supplying terminal 21. The inputs of a logic OR circuit are respectively connected to the output terminal of the first digit stage A and to the output terminal of the third digit stage C of the buffer register 14. The output of logic OR circuit 15 is connected to an output terminal 16 for supplying an output for driving the motor 6. The the output terminal of the first digit stage A and the output terminal of the fourth digit stage D are connected to a logic AND circuit 17, the output of which is connected to an output terminal 18 connected to supple a print instruction signal to the recording head.

Operation of the control circuit with reference to the time chart of FIG. 3 is now explained. For convenience of explanation, let it be assumed that a first word on a first line of a recording paper is already printed, the recording head is retracted for a distancecorresponding to two characters after one word has been printed, and then printing is restarted after advancing the recording head for a distance corresponding to three characters. Through the operation of the input section 1 a print starting command signal is fed to the input terminal 12 of the flip-flop circuit 11 to cause the flip-flop circuit to be set as shown in FIG. 3c. At the time when a readout clock signal (FIG. 3b) is fed to the buffer register 14,

the digit stage A of the buffer register is set to produce an output as shown in FIG. 3d. This output is applied to the logic OR circuit 15 to give a driving instruction to the drive motor as shown in FIG. 3h while supplying a forward control signal as shown in FIG. 3(i) to the forward control signal supplying terminal 19 for the drive motor to cause the recording head 6 to be moved. By the subsequent clock signals the buffer register 14 is shifted subsequently to produce outputs as shown in FIGS. 3e, 3f and 3g. When an output is obtained from the fourth digit stage D, this output causes, together with the output of the first digit stage A, the logic AND circuit 17 to be operated to permit a print instruction to be initiated from the printing instruction output terminal 18 as shown in FIG. 3k. That is, subsequent to supplying the forward control signal to the drive motor the recording head is advanced in the forward direction for a distance corresponding to three charcters and printing is effected from the fourth character on. Thus, the recording head is retracted in the backward direction for-a distance corresponding to two characters after a predetermined word is printed, and printing is resumed for the next subsequent words with a space corresponding to one character left from the point in time at which the last word has been printed. Prior to the output of the printing instruction being supplied from the terminal 18 to the recording head, the recording head is moved by the drive motor before being advanced for a distance corresponding to three characters. During at least a portion of this time, the speed of the recording head, at restart, will be non-uniform. At the time of printing the next successive words on the recording paper the recording head has accelerated and has reached a uniform speed at which correct printing can.

be effected. The printing is effected in the following manner. Suppose that a printing signal corresponding to one word consisting of five characters, for example,

CASIO is supplied through the buffer register 2 to the reset terminal 13 of the flip-flop circuit 11. Then, the output of the flip-flop circuit 11 becomes zero from the ninth character as shown in FIG. 3c. As a result, the output of the first digit stage A of buffer register 14 becomes zero since a clock signal 4), will no longer be present. The output of first digit stage A; of the buffer register 14 being zero causes one gate input of the logic AND circuit 17 (which has until now supplied a printing instruction signal) to be zero, thus blocking logic AND circuit 17 and; interrupting the supply of the printinginstruction signal as shown in FIG. 3k. At the end of this printing an output from the third stage C of the buffer register 14 is still being supplied to the logic OR circuit 15 and a drive control signal to the drive motoris being derived from the terminal 16. Under these conditions, the output of the first digit stage A switched over from the forward control signal supplying terminal 19 to the backward control signal supplying terminal 21 through the inverter 20 to cause the recording head to move in a backward direction. When the backward movement of the recording head is stopped at the digit C and a clock signal is present, the output of the digit C becomes zero as shown in FIG. 3f and the output of the logic OR circuit 15 becomes zero. As shown in FIG. 3h the motor is stopped after being retracted, for a distance corresponding to two characters at the end of printing. Such printing operation is repetitively, or cyclically, effected, word by word, and continued with a space corresponding to one character left for each word. Therefore, printing is not effected simultaneously with the restart of the motor. In other words, printing is effected after the recording head is moving at uniform speed, with the result that neither deformation of characters nor excess spacing between words are encountered during the printing operation.

The embodiment of FIGS. 4 and 5 will now be explained. In this embodiment, the recording head 6 is moved in the backward direction immediately before a printing instruction is made. Then, the recording head is controllably moved in the forward direction. During the time period so spent, the recording head is first accelerated so that it is moving at uniform speed, and then printing is effected.

In a control circuit as shownn in FIG. 4, the output terminal of a flip-flop circuit 31 having a set input terminal 32 and a reset output terminal 33 is connected to a first digit stage A of a buffer register 34 consisting of six digit stages A, B, C, D, E and F. A conventional source 44 of clock signals and 4: is coupled to buffer register 34. The output of the first digit stage Aand the Q output of the flip-flop circuit 31 are respectively connected to the input terminals of a logic AND circuit 35, the output of which is connected to a driving signal supply terminal 37 for the drive motor. The output of the third stage C of the buffer register 34 is connected to an input of logic AND circuit 36 through an inverter 38 and the other input of logic AND circuit 36 is connected to the output terminal of the first digit stage A of the buffer register 34. The output of the logic AND circuit 36 is connected to a backward control terminal 39 for the drive motor and through an inverter 40 to a forward control terminal 41 for the drive motor, respectively. Connected to a sixth digit stage F of the buffer register 34 and the Q output terminal of the flipflop circuit 31 is a logic AND circuit 42, the output of which is connected to a print instruction supplying terminal 43 for supplying a print instruction signal to the recording head.

The control circuit of FIG. 4 is operated as shown in the time chart of FIG. 5.

The recording head is moved, by suitable energization of the drive motor, in a backward direction for a distance corresponding to two characters before a printing instruction signal is fed to the recording head. Then the rotational direction of the drive motor is reversedimmediately and the recording head is advanced in a forward direction for a distance corresponding to three characters. Thereafter, printing is effected from the fourth character on, and the recording head is stopped simultaneously at the end of printing.

Input section 1 as shown in FIG. 1 provides a print start command signal to the gate input terminal 31 of the-flip-flop circuit 32 to cause it to be'in the set condition as shown in FIG. (c). At the time a clock signal q5 (FIG. 5b) for operating the buffer register 34 is obtained, the digit stage A of the buffer register 34 is caused to be set as shown in FIG. 5d to produce an output from the first digit stage A. The output of the least significant digit (i.e., stage A of register 34) is applied, together with the output of the flip-flop circuit 31, to the logic AND circuit 35 to generate a drive control signal to motor 7 from the terminal 37 as shown in FIG. 5j. At this time an output from the digit stage C does not appear, and an output from the inverter 38 is impressed on the logic AND circuit 36 to generate an output, causingthe recording head to move in a backward direction, as shown in FIG. 5k, by the drive motor. When the buffer register 34 is sequentially shifted and an output appears at the digit stage C, the inverter 38 is reversed and the output of the logic AND circuit 36 becomes zero as shown in FIG. 5k. Then, the drive motor is rotated in the reverse direction to permit the recording head to be advanced in a forward direction as shown in FIG. 51. During the advance of the recording head, the buffer register 34 is sequentially shifted. When an output appears at the sixth digit, then the out put of the sixth digit stage F is applied, together with the output of the flip-flop circuit 31, to the logic AND circuit 42 to supply a print instruction signal from the terminal 43 to the recording head as shown in FIG. 5i

and printing is started as shown in FIG. 5m. Thus, after the recording head is moved in the backward direction for a distance corresponding to two characters, the drive motor is reversed and the recording head is advanced in the forward direction for a distance corresponding to three characters and printing is effected from the fourth on. When a print end signal is applied to the reset terminal of the flip-flop circuit 31 from the buffer register 2 as shown in FIG. 1 in which a printing content is stored, the flip-flop circuit 31 is rendered in the reset condition. Each time the clock signal is provided as shown in FIGS. 5d, 5e, 5f, 5g and 5h the sequential shift is made and a output then becomes zero. When the output of the flip-flop circuit 31 becomes zero, the output of the first digit stage A of the buffer register 34 becomes zero and a drive signal to the drive motor no longer appears at the terminal 37 as shown in FIG. 5j. Then the advance of the recording head in the forward direction is stopped as shown in FIG. 5!. Since the output of the logic AND circuit 42 is not present, printing is also stopped as shown in FIG. 5m. In the above-mentioned embodiment, immediately before a printing instruction signal is made the recording head is retracted in the backward direction and then the drive control of the drive motor is actuated to permit the recording head to be advanced in the forward direction and printing is effected; that is, when the recording head has already attained its uniform speed before printing instruction is given.This embodiment thus also attains the intended object.

What is claimed is:

1. An ink jet type printing device comprising;

an input section (1) providing character signals and controlling printing;

a recording-head section (6) including an printing means;

a drive motor (7) driving the recording head section a drive motor control section (8,9) controlling the rotation of the drive motor (7 in both rotary direc- 4 tions;

a character signal generating section (4,5) supplying a deflection-controlled character signal ,to the v printing means;

a print command supplying control section (3) for controllably supplying a print command signal to the character signal generating section (4,5);

a register (.2) for storing desired print information, connected to and supplied by an input signal from the input section (1) the output of the register (2) being coupled; to the print command supply control section (3);

and a control circuit means (9) connected to the input section (1), and providing output control signals to the print command supplying control section (3), the control circuit means (9) including means responsive to input signals from the input section (1) for providing command signals to the motor control section (8,9) for causing the motor control section to controllably excite the motor to move the record head section (6) first backward and then forward for a specific distance before the printing means starts printing characters, and thereafter providing output control signals to the print command supplying control section 3) to enable printing of the information in said register, to thereby prevent non-uniform printing due to initial non-uniform speed of the recording head upon start of movement of the recording head section (6).-

2. The ink jet type printing device as claimed in claim 1 in which said control circuit means (9) includes a control flip-flop circuit means (FIG. 4: 31) connected to be set by a drive starting signal from the input section (1: 32,33);

and a shift register ('34) comprising a plurality of stages to store and shift bits from the least significant digit to the most significant digit and having a first output terminal (A), at the least significant digit position, connected to selectively supply a backward and a forward command signal to the motor control section (8,9) and hence to the motor (7 a second output terminal (F) at the most significant digit position connected to the print command supplying control section (3) to .supply a print instructing signal to the control section (3). 3. The ink jet type printing device as claimed in claim 2 in which said control flip-flop circuit (31) is reset by a print end signal, said least significant digit of said shift register (34) is reset in response to the reset signal from the control flip-flop circuit (34), said flip-flop circuit (31) being connected to the drive motor control secink jet tion (8,9) to supply a backward command signal to the drive motor (7) to cause the drive motor to be moved in a backward direction by the reset of the least significant digit of the shift register (34), said backward movement of the drive motor being effected until a predetermined stage (C) corresponding to an intermediate digit of said register (34) is reached.

4. An ink jet type printing devicee comprising:

an input section (1) providing character signals and controlling printing;

a recording head section (6) including ink jet mg means;

a drive motor (7) driving the recording head section a drive motor control section (8,9) controlling the rotation of the drive motor (7) in both rotary directions;

a character signal generating section (4,5) supplying a deflection controlled character signal to the printing means;

a print command supplying control section (3) for controllably supplying a print command signal to the character signal generating section (4,5);

a register (2) for storing desired print information, connected to and supplied by an input from the input section (1) the output of the register (2) being coupled to the print command supplying control section (3);

and a control circuit means (9) connected to the input section and providing output control signals to the print command supplying control section (3), the control circuit means (9) including means responsive to input signals from the input section print- (1) providing command signals to the motor control section (8,9) for causing the motor control section to controllably excite the motor to move the record head section (6) first forward for a specific distance, upon sensing of a character signal commanding the printing of characters, and thereafter providing output control signals to the print command supplying control section (3) to enable print ing of the information in said register, and then backward after the printing of a word, to thereby prevent non-uniform printing due to initial nonuniform speed of the recording head section upon restart of movement of the recording section (6).

S. The ink jet type printing device as claimed in claim 4 in which said control circuit means (9) includes a control flip-flop circuit (FIG. 2: 11) connected to and being set by a drive starting signal from the input section (1: 12,13);

a shift register (14) comprising a plurality of stages to store and shift bits from the least significant digit to the most significant digit and having a first output terminal (A) at the least significant digit position connected to selectively supply a forward and backward command signal to the motor control section (8,9) and hence to the drive motor (7), a second output terminal (C) at an intermediate digit position connected to supply a drive command signal to the motor control section (8,9) and a third output terminal (D) at the most significant digit position connected to supply the output control signal to the print command supplying control section UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,925,787 DATED 3 December 9, I975 VENT0R S Masahiko SUZUKI It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the initial page of the patent, change the address of the Assignee from "Yamato, Japan" to Tokyo, Japan-;

Column 6, line 27, after "being coupled" delete Column 7, line 7, after "digit of said" insert --Shift-;

line 8, change "devicee" to -device.

Signed and gc'alcd this twentieth Day Of April1976 [SEAL] RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmixsimu'r nj'lau'nls and Trademarks 

1. An ink jet type printing device comprising: an input section (1) providing character signals and controlling printing; a recording head section (6) including an ink jet printing means; a drive motor (7) driving the recording head sectIon (6); a drive motor control section (8,9) controlling the rotation of the drive motor (7) in both rotary directions; a character signal generating section (4,5) supplying a deflection-controlled character signal to the printing means; a print command supplying control section (3) for controllably supplying a print command signal to the character signal generating section (4,5); a register (2) for storing desired print information, connected to and supplied by an input signal from the input section (1) the output of the register (2) being coupled; to the print command supply control section (3); and a control circuit means (9) connected to the input section (1), and providing output control signals to the print command supplying control section (3), the control circuit means (9) including means responsive to input signals from the input section (1) for providing command signals to the motor control section (8,9) for causing the motor control section to controllably excite the motor to move the record head section (6) first backward and then forward for a specific distance before the printing means starts printing characters, and thereafter providing output control signals to the print command supplying control section (3) to enable printing of the information in said register, to thereby prevent non-uniform printing due to initial non-uniform speed of the recording head upon start of movement of the recording head section (6).
 2. The ink jet type printing device as claimed in claim 1 in which said control circuit means (9) includes a control flip-flop circuit means (FIG. 4: 31) connected to be ''''set'''' by a drive starting signal from the input section (1: 32,33); and a shift register (34) comprising a plurality of stages to store and shift bits from the least significant digit to the most significant digit and having a first output terminal (A), at the least significant digit position, connected to selectively supply a backward and a forward command signal to the motor control section (8,9) and hence to the motor (7); a second output terminal (F) at the most significant digit position connected to the print command supplying control section (3) to supply a print instructing signal to the control section (3).
 3. The ink jet type printing device as claimed in claim 2 in which said control flip-flop circuit (31) is reset by a print end signal, said least significant digit of said shift register (34) is reset in response to the reset signal from the control flip-flop circuit (34), said flip-flop circuit (31) being connected to the drive motor control section (8,9) to supply a ''''backward'''' command signal to the drive motor (7) to cause the drive motor to be moved in a backward direction by the reset of the least significant digit of the shift register (34), said backward movement of the drive motor being effected until a predetermined stage (C) corresponding to an intermediate digit of said register (34) is reached.
 4. An ink jet type printing devicee comprising: an input section (1) providing character signals and controlling printing; a recording head section (6) including ink jet printing means; a drive motor (7) driving the recording head section (6); a drive motor control section (8,9) controlling the rotation of the drive motor (7) in both rotary directions; a character signal generating section (4,5) supplying a deflection controlled character signal to the printing means; a print command supplying control section (3) for controllably supplying a print command signal to the character signal generating section (4,5); a register (2) for storing desired print information, connected to and supplied by an input from the input section (1) the output of the register (2) being coupled to the print command supplying control section (3); and a control circuit means (9) connected to the input section and providing output control signals to the print command supplying control secTion (3), the control circuit means (9) including means responsive to input signals from the input section (1) providing command signals to the motor control section (8,9) for causing the motor control section to controllably excite the motor to move the record head section (6) first forward for a specific distance, upon sensing of a character signal commanding the printing of characters, and thereafter providing output control signals to the print command supplying control section (3) to enable printing of the information in said register, and then backward after the printing of a word, to thereby prevent non-uniform printing due to initial non-uniform speed of the recording head section upon restart of movement of the recording section (6).
 5. The ink jet type printing device as claimed in claim 4 in which said control circuit means (9) includes a control flip-flop circuit (FIG. 2: 11) connected to and being ''''set'''' by a drive starting signal from the input section (1: 12,13); a shift register (14) comprising a plurality of stages to store and shift bits from the least significant digit to the most significant digit and having a first output terminal (A) at the least significant digit position connected to selectively supply a forward and backward command signal to the motor control section (8,9) and hence to the drive motor (7), a second output terminal (C) at an intermediate digit position connected to supply a ''''drive'''' command signal to the motor control section (8,9) and a third output terminal (D) at the most significant digit position connected to supply the output control signal to the print command supplying control section (3). 